In: Statistics and Probability
Walmart Company surveyed the senior managers in the retail industry
to understand their mean annual salary. A random sample of 49
managers reviled a sample mean of $45420. The standard deviation of
this population is $2050. Calculate the 95% confidence interval
estimate.
Solution :
Given that,
 = 45420
 = 2050
n = 49
At 95% confidence level the z is ,
 = 1 - 95% = 1 -
0.95 = 0.05
 / 2 = 0.05 / 2 =
0.025
Z
/2 =
Z0.025 = 1.96
Margin of error = E = Z
/2* (
 /n)
= 1.96 * (2050 / 49)
= 574
At 95% confidence interval estimate of the population mean is,
 - E < 
 < 
 + E
45420 - 574 < 
 < 45420 + 574
44846 < 
 < 45994
($44846 , $45994)